Heating of fluids



Jan. 4, 1944.v l.. A. MEKLER 2,338,295 Y HEATING OF FLUIDS Filed April 25, -1941 2 Sheets-Sheet 1 Patented Jan. 4, 1944 HEATING F FLUIDS Lev A. Mekler, Chicago,

Oil Products Company, Chi

tion o! Delaware Ill., assignor to Universal cago, Ill., a corpora- Application April 25, 1941, Serial No. 390,223

7 Claims.

The invention relates to an improved form of heater for fluids which, although not limited thereto, is particularly advantageous for heating hydrocarbon oils and/or gases to the high temperatures required in thermal and catalytic conversion processes.

The improved form of heater provided by the invention is of the general type having a fired Wall over which a substantially continuous sheet of flames and hot combustion gases is directed and having a fluid conduit comprising a plurality of interconnected tubular elements spaced from said wall and extending either substantially parallel or. transverse to the general direction of firing, said tubes being disposed to receive radiant heat from the fired wall and from the names and hot combustion gases passing thereover.

Heaters of this general type are particularly advantageous in quickly heating fluids to relatively high temperatures due to the relatively high rates of heat -transfenobtainable therein and, although not limited thereto, are particularly useful in quickly heating hydrocarbon oils v and hydrocarbon gasesv to the relatively high temperatures required for their pyrolytic or catalytic conversion. Their chief disadvantage resides in the fact that materially reduced rates of heat transfer are ordinarily obtained 'in that portion of the tube bank or fluid conduit most remote from the source of the flames and hot combustion gases due to cooling of the latter as they pass over the red wall and, further, that relatively poor thermal efflciency is obtained except when a separate tube bank or other fluid conduit is provided in the path of flow of the partially cooled combustion gases leaving the 'combustion and radiant heating zone, much useful heat in these gases being otherwise lost.

The improved form of heater andthe improved method of heating provided by the invention obviates the aforementioned disadvantages of heaters of the 'general type to which the invention is addressed by providing for increasing the fluid heat component supplied from the combustion gases to the tube bank in that portion of the latter which receives the smaller increment of Vradiant heat (i. e., that portion which is most remote from the source of the flames and hot combustion-gases): This is accomplished by providing spaced refractories in close proximity to -thatportion of the tubular elements most remote from Ythe source of the flames and hot combustion gases and causing the combustion gases, which have given up a major portion of their radiant heat to the fired wall and to the other portions ofthe tube bank, to pass about and in intimate contact with said remote portion of the tubes at relatively high velocity through the spaces provided between the refractory shapes and between the refraction of the readily available fluid heat in the` tory shapes and the tubes. Thus, a large porcombustion gases is transmitted to that portion of thev tube bank which receives the smallest increment of radiant heat and the rate of heat transfer is materially increased in this portion of the tube bank.

The accompanying drawings diagrammatically -illustrate Severn specific -embodiments of the improved form of heater provided by th'e invention, in each of which the improved method of heatingv provided by the invention may be accomplished.

Fig. 1 represents a sectional elevation of a downwardly fired vertical heater employing two banks of vertically disposed tubes.

Fig. 2 is a sectional yview of a portion of a heater illustrated in Fig. 1, this section being taken along the plane indicated by line 2--2 in Fig. 1.

Fig. 3 is a diagrammatic side elevation of a heater, such as illustrated in Fig. 1, showing the attachment of a convection section thereto.

Fig. 4 is a diagrammatic plan view of the heater illustrated in Fig. 3.

Fig. 5 of the drawings represents a sectional end elevation of a downwardly fired vertical heater employing a single bank of vertically disposed tubular elements.

Referring now illustrated comprises a structural steel framework, of suitable conventional form, part of the members of this framework being here shown and designated by the reference numeral l. Suitable A`refractory shapes of fire-brick or the like, for example, are suspended from or attached to the steel framework in a conventional manner, not illustrated, to form the side walls 2 and 3, the roof 4 and the sloping walls 5 and 6.

The fluid 'conduit herein provided comprises two vertical rows of vertically disposed tubes 1 extending between the roof 4 and floor 8 of the heater. In the particular case illustrated. the tubes of each row terminate at their upper ends in headers 9, to one of which the fluid to be heated is supplied by well known means, not illustrated, while heated fluid is discharged from the other, these headers being. disposed outside the heated zone of the furnace. Pairs of tubes in the two-.rows are interconnected at their lower ends, in the case here illustrated, by means of fittings I0 and cross-over conduits Il, also disposed outside the heated zone, whereby the two rows of tubes form a plurality of substantially U-shaped fluid conduits through which separate streams of the fiuid to be heated, of substantially equal volume, are passed in parallel from the vinlet header to the outlet header. It is, of course,

within the scope `of the invention to provide headers at the loweras well as the upper ends of the tubes to obtain a greater number of paralto Figs. 1 and 2, the heater here l lel streams of the same or different fluids. Also, the cross-over connection between adjacent tubes in different rows may be disposed at the top rather than the bottom thereof. The fittings I here illustrated may also be replaced, when desired, by elbows or tube bend ttings or a single substantially U-shaped bend may be sub# stituted for the fittings and conduit Il. shaped bend' or similar stream-line connection is contemplated when the iluid undergoing heat treatment is of such a nature, or the heating conditions to whichit is subjected are of such a nature, that deposits such as carbonaceousl or calcareous materials, for example, do not accumulate in the tubes and 'necessitate periodic cleaning of the latter. In case deposits which must periodically be removed accumulate in the tubes, I preferably employ fittings, such as indicated,l for example, in the drawings -which have ports and removable closure means therefor opposite the ends ofvtubes 'I and conduits II to Au-A give access thereto for cleaning. 'Ihe headers 9 are also preferablyv provided in such cases with a cleaning port and removable closure means therefor opposite the end of each tube.

The two rows of tubes are, as indicated in the drawings, spaced from each other and from the side walls 2 and 3, providing combustion and heating zones I2 and I3 between the respective side walls 2 and 3 and the adjacent row of tubes and providing 'a suncient space between the tube rows to accommodate a combustion gas passageway' I4 adjacent the lowerend thereof.

' The combustion and heating zones I 2 and I3 are separately red by means of burners I5 and ring ports I6 arranged in rows adjacent the side walls and so disposed that flames and hot combustion gases resulting from the combustion of fuelair mixtures is supplied through the firing ports, impinging against the refractory side walls in the form of substantially continuous sheets, heating the side walls and l particularly their upper portions to a highly radiant condition.

Except when little or no excess air is supplied to the combustion and heating zones, in a heater of the nature illustrated, substantially higher temperatures' will prevail in the upper than in the lower portion thereoLfwith lthe result that a considerably greater amount of heat will be transmitted from the names and from the hot refractory side walls to the upper portion ofthe tubular elements, as compared with the radiant heat supplied to the lower portion thereof. This condition gives lower rates of heating at the lower ends of the tubes as compared with the n desirable high rates obtained tion thereof. Y

One of -the objects of the present invention irr the upper p01- amount of radiant heat transmitted theretoand thus accomplishes the aforementioned object.

Referring now to Fig. 2, which illustrates the construction of the refractory side Walls I 1 of the combustion gas passageway I4, it will'be noted that the-refractory shapes which formthese walls are 'spaced a short distance apart and provided with a contour along their adjacent outer edges substantially conforming to that of the tubes l, so that the combustion gases passing from 'the combustion and heating zones I2 and v would otherwise prevail, whereby the'vradiant energy imparted therefrom to the adjacent surfaces of tubes 1 is materially increased.

The combustion gases discharged from heating zones I 2 and I3 pass through the flue or combustion gas passageway I4 to a suitable stack and, when desired, they may, as indicated in Figs. 3 and 4, pass during their course of travel from zone I 4 to the stack through a convection or fluid heating zone which serves as-an economizer section to recover addtional available heat from the combustion gases. l

In Figs. 3 and 4, the main furnace structure is indicated diagrammatically at 2I and the comis to provide a heater wherein more uniform high ratesof heating are obtained throughout the tube bank and from top to. bottom ci' the com- .f bustion and heating zone without the necessity of eliminating excess air or reducing it to the point whereexcessively high combustion gas temperatures prevail at the exit from the combustion and heating zone. To accomplish this, I provide means for passing the combustion gases leaving the heating zone in intimate contact at relatively high Yvelocity with that portion of the tube bank wherein radiant heatingwis materially reduced. VThe increased amount of uidV heat thus imparted to this portion of the bank .by scrubbing it with the hot combustion gases leaving the combustion and heating zone compensates to a large degree for the decreasedl fluid heating zone es tional combustion gases,

bustion gas passageway -I4 of Fig. 1 terminates in a portion 22 disposed outside the main furnace structure which connects passageway I4 with the fluid heating zone 23, shown in crosssection in Fig-3, above which stack 24 is mounted. A checker-work wall 25 is provided, in the casehere illustrated, adjacent the exit of portion 22 of the combustion gas passageway to distribute the `combustion gases substantially uniformly across the lower portion of the structure comprising huid heating zone 23. A bank of fluid `tubular conduits 26, illustrated in cross-l 4 section in Fig. 3,' is provided within fluid heating zone 23, this tubebank comprising, in the case here illustrated, a plurality of superimposed horizontal rows of horizontally disposed tubes. The combustion gases passing from zone 22 to stack 24 through fluid heating zone 23 pass about and in direct contact with the tubular elements 26 and supply heat to the fluid passing therethrough, which latter may be the same or a differert fluid than that supplied to tubes 1 of Fig.

When desired, I provide for supplying addipreferably at va, higher temperature than those from passageway I4, to

`23 to increase the heat supplied to tubes 26. This may be accomplished,

, for example, 4by providing one or a plurality of burners indicated at 21 inFig. 3 andl burner ports indicated at 28 in Fig. @communicating with portion 22 of the combustion gaspas'sageway through the top of the latter, although they may be provided at any point in lthe combustion gas passageway or huid heating zone' between the tube bank in the latter and the main furnace structure.

Referring now to Fig. 5, the single cell clown-- nred heater here illustrated is, in most respects,

approximately one-half of the structure illustrated in Fig. 1, except that the vertical bank of vertically parallel tubes I are disposed adjacent the refractory side wall 52, the opposite refractory side wall 53 being ilred in substantially the same manner as side walls! and 3 of Fig. 1 by means of burners 54 and burner ports,55 provided in the roof 56.

The tubes 5I extend between and through the roof 56 and the iloor 51 of the heater and may terminate in suitable headers or return bends, :biot illustrated, connecting adjacent tubes of the The lower portion of wall 52 of this heater is constructed in the same manner as side walls I1 of the combustion gas passageway Il in Fig. 1 (for details see Fig. 2). An extension oi floor 51 an extension of one of the end wallsof the heater, not illustrated, a refractory wall 58 parallel to and spaced from the lower portion of wall 52 and a top wall 59 form a ue or combustion gas passageway 60 to which combustion gases are supplied from the combustion and heating zone 6l and wherethrough they pass to a stack, not shown, or to a suitable fluid heating or economizing section similar, for example, to that illustrated in Figs. 3 and 4.

I claim as my invention:

1. A heater for fluids comprising, in combination, a heating zone, means for passing hot combustion gases vertically through the heating zone from adjacent one end thereof to adjacent its opposite end, a combustion gas passageway communicating with'the heating zone adjacent said opposite end of the heating zone, a bank of tubular fluid conduits dispsed in said heating zone to receive heat by radiation from said hot-combustion gases, a portion of each being disposed outside the main' path of travel tube of said bank J of said hot combustion gases passing through the heating zone and a partition provided with re.-

stricted openings between the heating zone and the combustion gas passageway in registration in the direction of gas ilow with other portions of the tubes inj said opposite end of the heatingzone.

2. A heater lfor fluids comprising, in combination, a heating zone, means for passing hot combustion gases vertically through the heating zone from adjacent one end thereof to adje-cent its opposite end, a combustion gas passageway a partition provided with restricted openings between said passageway and the heating zone adjacent said opposite end of the heating zone, a bank of substantially vertical tubular fluid conduits disposed in said heating zone to receive heat by radiation fromy the stream of hot combustion gases passing therethrough, that portion of each tube of said bank which is exposed to radiation from the hottest portion of said stream being disposed outside the main path of flow of the latter and one of said restricted openings being in registra.'- tion in the direction of gas ow with that portion of each tube of said bank 'which is exposed to radiation from the cooler portion of said stream.

3. A heater for fluids comprising, in combination, a heating zone, means for passing hot combustion gases vertically through the heating zone from adjacent one end thereof to adjacent its opposite end, a combustion gas passageway apartition provided with restricted openings between said passageway and the heating zone adjacent said opposite end of the heating zone, a bank of named wall adjacent one zones having oppositely substantially vertical tubular duid conduits disposed in said heating zone to receive heat by radiation from the stream of hot combustion gases passing through the latter, said restricted openings being in registrationrin the direction of gas iiow with end portions of the tubes of said bank whereby said end portions are swept by combustion gases passing to the combustion gas passageway from the heating zone, and the remaining portion of said tubes being disposed outside the main path of flow of the stream 0f combustion gases passing through the heating zone.

4. A heater for fluids comprising, in combination, a combustion and heating zone having a bare tired wall, means for passing' flames and hot combustiongases longitudinally along said wall to heat the same to a radiant condition, an opposite unflred wall, a bank of fluid tubular conduits disposed along the length of and adjacent said uniired wall, restricted openings in the lastend thereofr through which communication is established between the heating zone and a combustion gas passageway associated therewith and said openings being in registration with the tubes in the direction of flow of combustion gases from the heating zone to said passageway. f l

5. A heater f or fluids comprising, in combination, a radiant heating zone h'aving oppositely disposed red walls, means-for passing iiames' and hot combustion gases surfaces of saidwalls to heat the same toa radiant condition, spaced apart rows of tubular fluid conduits disposed within said heating zone substan- -tially parallel to and spaced from said walls, a combustion gas'passageway disposed` between the tube rows and adjacent one end thereof, said passageway having walls substantially parallel to the tube rows and provided with restricted openings in registration with the tubes in the direction of flow of combustion gases'from the radiant heating zone to said passageway.

' 6. A heater for iluids comprising,in combination, separately red combustion and heating disposed red walls, means for passing flames and hot combustion gases vertically over said iired 'walls to heat the same to a radiantscondition, a fluid conduit comprising separate, spaced apart, substantially vertical rows of tubes spaced from said fired walls in the combustion and heatingzones, a combustion gas passageway being provided between said rows and having walls with restricted openings in registration with the tubes in the direction of flow of combustion gases from the combustion and heating zones to said passageway.

7. A heating apparatus comprising a chamber, means for introducing hot combustion prod ucts to the chamber adjacent one end thereof, ai combustion gas discharge passageway 'adjacent the opposite end of the chamber, heating tubes extending between said ends 0f the chamber and disposed to receive radiant heat from the combustion gases passing through the chamber, a refractory wall adjacent but spaced from the portions of the tubes near said opposite end of the chamber and forming an obstruction lbetween the chamber and said passageway, and restricted openings in said wall in registration with the tubes in the direction of4 ing communication between -.the chamber and said passageway, whereby combustion gas streams are passed over saidportions of the tubes at relatively high velocity.

LEV A. MEKLER.

longitudinally over the inner` gas flow and establish- 

